Basically, our objective is to determine the number and type of hypothalamic releasing and inhibiting hormones by isolating them from porcine hypothalami, an objective that we feel cannot be definitively and expeditiously realized by any other approach. Since we have obtained substantial chemical and biological evidence that FSH-RH may exist in the hypothalamus and some biological and chemical evidence for hypothalamic hormones or substances that inhibit LH and/or FSH release and that stimulate ACTH release, studies have been outlined for the isolation of the putative hypothalamic hormones, FSH-RH, LH-IH as well as CRH in order that they can be chemically identified and synthesized. The hormonal activities will be determined in vitro and in vivo. Characterization of these hormones or substances will consist of comparing the activities of crude, partially and highly purified hypothalamic preparations and also will consist of determining the following: biological activities as related to age, sex and species of animals, specificity of activity, time-response relationships, dose- response relationships, inactivation by serum, interaction with other hormones, relationships to cyclic AMP and other substances found to alter pituitary cyclic AMP levels and the effects of theophylline, cations, cycloheximide, etc. The realization of our objective is of fundamental importance for understanding the normal regulation of pituitary hormonal secretion.